The present invention relates generally to film deposition and more particularly to a method and apparatus for reducing target arcing during metal film deposition.
Metal films are used widely within semiconductor integrated circuits to make contact to and between semiconductor devices (i.e., metal interconnects). Because of the high densities required for modern integrated circuits, the lateral dimensions of interconnects, as well as the lateral dimensions between interconnects, have shrunk to such a level that a single defect can destroy an entire wafer die by shorting a junction region or open-circuiting a gate electrode of an essential semiconductor device. Defect reduction within interconnect metal films, therefore, is an ever-present goal of the semiconductor industry that increases in importance with each generation of higher density integrated circuits.
Interconnect metal films typically are deposited via physical vapor deposition within a plasma chamber, and more recently via high density plasma (HDP) deposition. In both processes, a target of to-be-deposited material (e.g., the metal comprising the interconnect) is sputtered through energetic ion bombardment that dislodges atoms from the target. The dislodged atoms travel to a wafer disposed below the target and form a metal film thereon. Thereafter the metal film is patterned to form the interconnect.
Ideally the metal film is highly uniform and defect free. However, a substantial number of blobs or splats of target material appear within thin films formed by sputter deposition within conventional sputtering chambers. These splats are believed to result when a phenomenon known as target arcing occurs (e.g., due to arc-induced localized heating of the target that melts and liberates a portion of the target material as described below).
Accordingly, a need exists for a sputtering target and/or sputtering chamber that reduce target arcing.
The present inventors have discovered that the flow of concentrated gas from sputter deposition chamber sealing surfaces can result in target arcing, and defect (e.g., splat) formation that accompanies such target arcing. Specifically, conventional sputter deposition chambers typically employ sealing surfaces having grooves with sealing members (e.g., o-rings) disposed therein to form a vacuum seal. For example, a sealing surface having a groove and a sealing member disposed therein may be employed to form a vacuum seal between a sputtering target assembly and the sidewalls of a vacuum chamber when the sputtering target assembly serves as a chamber xe2x80x9clidxe2x80x9d. Because gas may become trapped within the groove of such a sealing surface (and negatively affect the vacuum seal of the sealing surface), relatively large xe2x80x9cvent slotsxe2x80x9d often are provided to the sealing surface that vent the trapped gas from the sealing surface into the vacuum chamber.
The present inventors have found that conventional vent slots significantly concentrate the flow of trapped gas from sealing surface grooves into a vacuum chamber. This concentrated, trapped gas creates a high gas partial pressure along a few paths within the vacuum chamber and can lead to target arcing as described below. Defect formation that accompanies such target arcing thereby is increased.
To reduce target arcing due to the venting of trapped gas from sealing surfaces, the present invention preferably restricts the flow rate of trapped gas from sealing surfaces and/or increases the number of paths available for removing trapped gas from sealing surfaces.
Trapped gas concentration with a vacuum chamber thereby is decreased, and the likelihood of target arcing (and defect formation associated therewith) is decreased.
In a first aspect of the invention, a sealing surface of a sputter deposition chamber is provided with a groove adapted to receive a sealing member. The groove comprises an inner wall (i.e., a wall closest to the interior of the sputter deposition chamber) having a plurality of restrictive openings configured to restrict the flow of gas from the groove through the plurality of restrictive openings so as to reduce target arcing during a plasma process within the sputter deposition chamber.
In a second aspect of the invention, a method is provided for reducing defect formation during plasma processing. The method comprises providing a sputter deposition chamber having at least one sealing surface; and restricting the flow of gas from the at least one sealing surface into the sputter deposition chamber so as to reduce target arcing during sputter deposition within the sputter deposition chamber.
Other objects, features and advantages of the present invention, as well as the structure of various embodiments of the invention, will become more fully apparent from the following detailed description of the preferred embodiments, the appended claims and the accompanying drawings.